The present invention refers to a valve arrangement with at least one valve opening that can be sealed by a locking element.
For valves to be practical they must have high flow capacity and compact form. It is also important for a valve construction to have a low power requirement for overcoming the flow and positioning the valve to close off the flow. These requirements are of major importance when using valves in vacuum engineering. The manufacturing of integrated circuits, for instance, involves various steps that take place in vacuum processing systems. Depending on their specification, such processing systems are used for the manufacturing of thin films, for etching procedures, for procedures involving surface activation and for thermic and optical procedures. These procedures require, among other things, a very high purity of materials and environments. The smallest substrate contamination may bias the process and effect product quality or inhibit the manufacture of a functioning product at all. In this regard, the quality of the vacuum condition within which the processing takes place is also of major importance.
An expert is needed to dimension the vacuum system to create the necessary conditions in order to realize reasonably good results in vacuum quality. Both good vacuum conditions and economical product throughputs with such processing systems are mainly determined by the performance of the pumping system for creating the vacuum. In addition to correct dimensioning of the vacuum pump, special care is needed to keep pressure losses in valves and tubes of the system, as low as possible. It is often very difficult to meet these requirements when it comes to a practical construction of the system. If the tube configuration is unfavorably designed, losses within the tubes may increase to such an extent that the losses dominate the system and the influence of the pump becomes almost unapparent.
Vacuum systems with good pump performance thus, consist not only of efficient pumps but also of pump tubes with a high conductance or flow capacity. This requires relatively large sectional areas for the tubes. If valves are incorporated in the tubes, the transmitting sectional area across the valves must not reduce the conductance value. It is obvious that large tube sectional areas with the other needed specifications, require accordingly large valve opening sectional areas in order to keep losses low. Such large valve openings require high controlling forces to overcome the existing flow and pressure different which, in turn, requires both a robust valve construction and valve drive.
Because of these requirements, known valve constructions usually have large overall dimensions which considerably reduce the design possibilities for processing systems using the valves.
The high controlling forces linked to such valves create an additional problem. The forces must be held by appropriate bearings. Bearing problems in a vacuum environment are much more difficult to manage than other technical fields because of well-known lubrication problems. With extremely pure vacuum applications the use of lubricants is greatly reduced or may even be precluded altogether. In such a case, increased abrasion and therefore an increased generation of particles must be taken into consideration, especially where high friction forces exist. The generation of particles is greatly increased with high friction forces than with low ones.
When manufacturing micro circuits or when producing storage disks, such particles are not allowed due to the high purity requirement of such products. The existence of such particles means that, in the worst case, the product does not work and therefore is not usable. The planning and realization of such processing systems therefore include all possible precautions to prevent the generation of particles or to keep them at a controllable low level.
The U.S. Pat. No. 4,712,768 describes a "Butterfly" type valve. This type of valve is shown on a receptacle wall 7 in FIG. 2 herein. This valve 20 is incorporated with a cryo-pump 24 and is opened or closed by turning a valve plate 21 around a lateral axis (lying horizontally and in the plane of FIG. 2). Large tube diameters in this type of valve require a large diameter for valve plate 21. The size of this valve plate 21 then determines the necessary construction height of the arrangement as the necessary tilting area of the valve plate is given by its diameter. The pivot bearings have to absorb the entire force which mainly results from the pressure difference across the valve and the surface of the plate.
With this kind of valve, these forces dominate the friction and pressure forces of seals that are also needed in the valve. The high controlling forces require a relatively strong drive 22 which, with this kind of valve is incorporated laterally in the form of a rotating drive to rotate plate 21. Apart from the high construction height, such valves also require free space at the sides.
The industrial manufacturing of micro circuits by means of vacuum processing systems requires very compact system assemblies. This kind of system needs an expensive infrastructure in the buildings housing the system due to the required clean area conditions and the costly installations for the means needed to operate these systems. Today for instance, investment amounts of up to $10,000 to $20,000 per square meter are needed for construction of production areas in a manufacturing building having a class 10 clean area. The steadily increasing complexity of procedures also leads to more and more sophisticated equipment design. Economic reasons therefore dictate the use of compact assemblies (which thus require smaller clean areas) to meet increasingly high specifications.
A well structured compact system can also considerably improve maintenance and operability and thus guarantee economic operation and reliability of the system. The described systems often consist of numerous work stations with the result that several pumping systems have to be placed next to each other with only little space available. Valves as described in the aforesaid U.S. patent in many cases no longer meet these requirements.
Other known valves are disclosed in British patent specifications GB 1644/1909 and GB 1,550,459; French patents FR 965,427; FR 2,550,619; FR 1,532,450 and FR 1,322,491; German patent documents DE-U 8,812,723 and DE-C 1,193,432; and U.S. Pat. No. 4,520,846.
Of these, British patent specifications GB 1644/1909 and GB 1,550,459 and French patent FR 965,427 are material for showing sleeve shaped valve members that are movable to close the valve.
FIG. 1 herein shows another valve 19 which is known as a plate valve, where the valve plate 21, contrary to the valve 20 described in connection with FIG. 2, is not turned around a central axis, but is tilted in as a whole. Concerning compact design possibilities, this valve design has the same inconveniences as the one disclosed in FIG. 2. There is even an additional inconvenience in that the mechanism 22 for tilting the plate in requires much more effort than does the turning of the plate around a lateral axis.
In all the drawings, the same reference numerals are used to designate the same or similar parts.
FIG. 3 shows a schematic slide valve design 23. As shown in this figure, it is possible to design extremely flat valves. The problem is that the valve slider needs to pass a very long slide distance. The problems of compact design thus can not be solved optimally with this design. Due to high friction forces and large friction surfaces, the particle problem has an even higher impact in this design. German patent specification DE 3,209,217 disclosed such a slide valve.
In cases where a vacuum system requires pumps with high conductance or flow through values and/or extremely high pump values, the pumps 24 of FIGS. 1, 2 and 3 can be directly attached to the vacuum recipient chamber wall 7. Alternatively, they may be partly immersing in the vacuum chamber as shown at pumping device 12 in FIG. 4. This then is a practical solution in cases where no valving devices are required between the pump 24 and the processing chamber. FIG. 4 is a cross-sectional view of such a design. This arrangement is a commonly used cryo pump with cryo surfaces at 12 which form the pump element and which extend into the processing chamber. In this type of structure, due to the small spacing and good positioning of the pump elements in relation to the process, the pump is optimally positioned to achieve excellent results.
With many applications it is however necessary to separate the pumps from the chambers by valving devices 19, 20, or 23. These devices must, however, not degrade the optimum operational conditions provided by the kind of structure shown in FIG. 4.